This kind of contact type power feeding apparatus is known in, e.g., Patent Document 1. In this known apparatus, a power feeding apparatus is employed in inputting power to a cylindrical target in a rotary cathode unit for a magnetron sputtering apparatus. The power feeding apparatus is provided with: an inner cylinder body as a conductive axis body that is fixed to a predetermined position; an outer cylinder body (target) as a conductive cylinder body that is disposed coaxially in the circumference of this cylinder body; driving means for driving to rotate the outer cylinder body; and a brush which is disposed in a projecting manner on an outer peripheral surface of the inner cylinder body at a predetermined distance in an axial direction so that, as a result of rotation of the outer cylinder body, the inner peripheral surface of the outer cylinder body gets slid to thereby electrically conduct the two together.
In addition, an inlet port of a coolant is disposed in one end of the inner cylinder body and, also, an outlet port of the coolant is disposed on the other end on the inside of the outer cylinder body. It is thus so arranged that the coolant from the outlet port on the other end of the inner cylinder body is allowed to flow through the space between the inner cylinder body and the outer cylinder body, thereby flowing out of the coolant outlet port disposed in one end of the outer cylinder body. According to this arrangement, at the time of sputtering, not only can the target be cooled, but also can the dust and the like in the circulation passage be expelled from the coolant inlet port to the coolant outlet port.
In the above-mentioned kind of contact type power feeding apparatus, it is normal practice to select the material of the brush with respect to the material of the inner cylinder body and the outer cylinder body such that the brush preferentially wears. For this reason, the known apparatus has the following problems, namely, in an arrangement in which the brush is only disposed in a projecting manner on the inner cylinder body, when the contact surface of the brush with the outer cylinder body has worn out as a result of sliding movement of the brush, a problem arises in that the area of contact between the inner peripheral surface of the outer cylinder body with the brush becomes smaller. Or else, the inner peripheral surface of the outer cylinder body ceases to keep complete contact with the brush, resulting in failure to cause electric current to flow efficiently between the inner cylinder body and the outer cylinder body and, as a consequence, the lifetime of the apparatus in question comes to a premature termination. On the other hand, it is known to use, as a brush to be disposed between the inner cylinder body and the outer cylinder body, a coil material that has been formed into a spiral shape (see, for example, Patent Document 2). However, in this kind of arrangement it is difficult to secure the thickness in the radial direction of the brush itself, thereby resulting in a premature lifetime.